Condensation on windows, why they sweat and how to lubricate plastic window seals

Condensation on windows, often referred to as “sweating,” is a common issue, especially during colder months. It’s caused by a simple scientific principle: when warm, moist air comes into contact with a cold surface, the moisture in the air condenses into water droplets. Here’s a more detailed explanation and how to address it:  

Why Windows “Sweat”:

• Temperature Differences:
  • The primary cause is the difference in temperature between the warm, humid air inside your home and the cold surface of the window glass.
  • When warm, moist air touches the cold glass, it cools rapidly. This cooling causes the water vapor in the air to condense into liquid water.  
• High Humidity:
  • Activities like cooking, showering, and even breathing increase the humidity in your home.  
  • Poor ventilation traps this moisture, making condensation more likely.  
• Window Insulation:
  • Single-pane windows or poorly insulated double-pane windows are more prone to condensation because they have colder surface temperatures.  
  • Poorly installed windows, or windows with failing seals, will also contribute to greater condensation.  
• Air Tightness:
  • Modern, very well sealed windows, while great for energy efficiency, can also cause condensation issues, if the moist inside air is not dealt with, through ventilation.

How to Lubricate Plastic Window Seals:

Maintaining healthy window seals is important, here are some things to consider:

• Why Lubrication?
  • Window seals, particularly those made of rubber or plastic, can dry out and crack over time, losing their effectiveness.  
  • Lubrication helps keep them pliable, preventing cracks and ensuring a tight seal.  
• Lubricant Types:
  • Silicone-based lubricants: These are generally the best choice for window seals. They are non-reactive with most materials and provide long-lasting lubrication. Do not use petroleum based lubricants, as they will degrade the seals.  
  • Glycerin: In some cases, glycerin can also be used as a lubricant for rubber seals.
• Application:
  • Clean the seals: Before applying any lubricant, clean the seals with a damp cloth to remove dirt and debris.  
  • Apply lubricant: Apply a thin, even coat of the chosen lubricant to the seals using a clean cloth or sponge.
  • Wipe off excess: Remove any excess lubricant to prevent it from attracting dust and dirt.
• Frequency:
  • Lubricate the seals at least once a year, or more often if they appear dry or cracked.

Addressing Condensation:

• Improve Ventilation:
  • Open windows regularly, especially after activities that generate moisture.  
  • Use exhaust fans in kitchens and bathrooms.  
• Control Humidity:
  • Use a dehumidifier to reduce indoor humidity.  
  • Avoid overwatering indoor plants.
• Improve Insulation:
  • Consider upgrading to double- or triple-pane windows.
  • Ensure windows are properly sealed and caulked.
• Air Circulation:
  • Ensure that air can freely move around the windows. Sometimes, long curtains, or other obstacles, stop warm air from reaching the window surfaces.

By understanding the causes of window condensation and taking appropriate measures, you can create a more comfortable and healthy indoor environment.